1. Field of the Invention
The ability to be able to detect a wide variety of compounds at extremely low concentration with great specificity has provided substantial advances in diagnostic monitoring of drug administration.
In many fields, immunoassays have found application in detecting trace amounts of individual substances. The immunoassays are characterized by being able to detect a single substance at very low concentrations. However, in many situations, it is desirable to further increase the sensitivity. Other considerations involve minimizing background or unmodulatable signal, simplifying synthesis of the reagents; allowing for automation and finding application on a wide variety of conventional instruments and providing a simple protocol.
Among the immunoassays which have found widespread use are homogeneous enzyme immunoassays and homogeneous fluorescent immunoassays, where homogeneous intends the avoidance of a separation step in the assay, rather than having a single phase. These assays have found widespread acceptance and commercialization. However, there are still opportunities for further improvements in these assays in accordance with the above criteria or providing alternatives which may find preferred application in specific situations.
2. Description of The Prior Art
U.S. Pat. Nos. 4,256,834, and 4,275,149 and references included therein are illustrative of immunoassays. U.S. Pat. Nos. 3,855,987 and 4,108,972 describe labeled particles, particularly fluorescent labeled particles.